CVE-2026-85538: MISP Attribute Deletion Authorization Bypass Allows Users Without Modify Permissions to Delete Attributes
An incorrect authorization vulnerability in MISP allowed authenticated users to delete attributes from events despite lacking the required permmodify or permmodifyorg permissions.
The affected attribute deletion paths relied on organization membership checks performed by MispAttribute::deleteAttribute() but did not consistently enforce MISP's event modification authorization rules. Consequently, a user belonging to the organization associated with an event could potentially delete individual attributes or perform bulk attribute deletion even when their assigned role was not authorized to modify the event.
This created an inconsistency between attribute editing and deletion: editing an attribute correctly used MISP's ACL::canModifyEvent() authorization logic, whereas the affected deletion operations could bypass these permission checks.
An authenticated attacker with access to an affected MISP instance and membership in the organization owning an event could exploit this flaw to remove attributes from that event, potentially causing unauthorized modification or loss of threat intelligence data.
The patch introduces a common authorization check for all affected deletion paths. Before deletion, MISP now resolves the associated events and verifies that the current user is authorized to modify each event using the same authorization mechanism used by normal event and attribute modification operations.
Affected Software
Event History
Frequently Asked Questions
Who is realistically exposed to this issue?
Affected MISP instances are exposed to authenticated users who belong to the organization that owns an event. The user does not need event modification permissions if the vulnerable deletion path is available.
What does an attacker need to exploit the vulnerability?
An attacker needs an authenticated MISP account and membership in the organization associated with the target event. They can then target individual attribute deletion or bulk attribute deletion despite lacking perm_modify or perm_modify_org.
Are normal event editing permissions enough to prevent this?
No. The issue specifically affects deletion paths that did not consistently apply MISP's event modification authorization checks, while attribute editing used ACL::canModifyEvent() correctly.
What is the mitigation if patching cannot happen immediately?
Restrict access for users who are members of event-owning organizations but do not require attribute deletion capability, since organization membership may be sufficient to exploit the affected paths. Review and limit accounts with access to sensitive events.
How can defenders assess whether unauthorized deletion may have occurred?
Review attribute deletion activity, including bulk deletions, performed by users who lacked perm_modify or perm_modify_org for the affected events. The vulnerability could result in unauthorized removal of threat intelligence attributes.